A similar option called 5G Stand-Alone displays when you enable Show Advanced Settings:
The 5G Standalone setting becomes useful when you select Auto (all modes) in the Modem Connection Mode, while having a 5G modem. The available options are:
No Change: Allows a 5G capable modem to follow the default behavior of the network operator.
Disable: Prevents a 5G capable modem from connecting in 5G Standalone mode at any time, even when the network operator supports it.
Enable: Allows a 5G capable modem from connecting in 5G Standalone mode at any time if the network operator supports it.